Baculovirus protein expression in insect larvae provides a very useful, convenient, less labor-intensive and cost-effective system for the high- level production of proteins which may require a higher eukaryotic milieu for appropriate folding and/or post-translational modifications for biological activity. These in larva-produced proteins can be effectively used as veterinary diagnostics, therapeutics, vaccines, drug development, pesticides and antibody development. In our previous studies, we have been able to express various proteins in larvae by injection of recombinant baculoviruses. However, for the large-scale production of proteins in commercial markets, the efficiency of this system will be further improved by feeding the larvae with recombinant viruses instead of injection, as we have constructed a series of transfer plasmids for this purpose. In this project, we will set up this system and test the feasibility of this system for production of HBsAg in T. ni larvae with four specific aims: (1). to construct a recombinant transfer vector containing HBsAg; (2). to construct a recombinant AcNPV for larval feeding; (3). to feed larvae with recombinant AcNPV for production of HBsAg in T. ni larvae and (4). to purify HBsAg from haemolymph of infected larvae.